Abstract
Presented are results from a parametric investigation of wind-tunnel test-section configurations with a goal of stabilization of normal-shock-wave structure. The test section includes a two-flow-passage arrangement, where each passage is separated by a shock-wave-holding plate. The top wall for the top passage is contoured relative to the streamwise-flow direction, and a choking flap is located at the downstream portion of the bottom flow passage. Altered are the streamwise and spanwise positions of the shock-wave-holding plate, angle of the choking flap, and amount of venting. Of interest are shadowgraph flow visualization images, grayscale spectral energy variations, and integrated grayscale spectral energy levels. Higher static-pressure ratio downstream of the shock wave (caused by higher choking-flap angle, lower shock-wave-holding-plate position, and less venting) is associated with greater shock-wave-standoff distance (relative to the shock-wave-holding plate) and decreased flow unsteadiness. The most optimal arrangement includes a stabilized normal shock wave and lambda foot, which are largely two dimensional over the shadowgraph visualization volume.
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Abbreviations
- A :
-
Flow passage area
- A*:
-
Area in flow passage where Mach number is 1
- A min :
-
Minimum area in flow passage
- d :
-
Distance from test-section entrance to the shock-wave-holding-plate tip
- f :
-
Frequency
- Δf :
-
Frequency resolution
- F s :
-
Sampling frequency
- \( {\mathcal{F}} \) :
-
Fast Fourier transform function operator
- GS:
-
Grayscale value
- h :
-
Distance from the bottom wall to the shock-wave-holding plate
- \( \dot{m} \) :
-
Overall mass flow rate
- \( \dot{m}_{\text{b}} \) :
-
Mass flow rate in bottom flow passage
- \( \dot{m}_{\text{t}} \) :
-
Mass flow rate in top flow passage
- N :
-
Number of frames
- P e :
-
Static pressure in exhaust plenum
- P s :
-
Local static pressure in the test section
- P t :
-
Stagnation pressure at entrance of test section
- Str :
-
Strouhal number \( 2\pi f\delta/u_{\infty } \)
- t :
-
Time
- \( u_{\infty } \) :
-
Freestream velocity at entrance of test section
- θ :
-
Angle of the choking flap
- \( {\delta} \) :
-
Boundary layer thickness at entrance of test section
- y(t):
-
Digitized filtered time sequence at one pixel location
- Y(f):
-
Normalized Fourier transform of y(t)
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Acknowledgements
The Alabama Innovation Fund (Contract ID No. 61070000002), the University of Alabama Endowment Fund, and the Office of the Vice President for Research and Economic Development of the University of Alabama in Huntsville are acknowledged for financial support for the research which is reported in the present paper. The following individuals are also acknowledged for their assistance with laboratory development, laboratory testing, laboratory instrumentation and apparatus, and/or data analysis: Tony Hall, David Lineberry, Andrew Miller, Melissa Anderson, Robert Pertrimoulx, Daniel Corey, Soo Rhee, Conner Gisburne, Kaylee Hall, Sarah Stearman, Benjamin Shea, Benjamin Lund, Patrick McInturff, Connor Pierce, and Warren Buzzard.
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Communicated by A. Higgins.
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Ligrani, P.M., Marko, S.M. Parametric study of wind tunnel test section configurations for stabilizing normal shock wave structure. Shock Waves 30, 77–90 (2020). https://doi.org/10.1007/s00193-019-00911-5
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DOI: https://doi.org/10.1007/s00193-019-00911-5